Sunflowers' invisible colors help them attract bees and adapt to drought


Date:
January 18, 2022
Source:
University of British Columbia
Summary:
It turns out sunflowers are more than just a pretty face: the
ultraviolet colours of their flowers not only attract pollinators,
but also help the plant regulate water loss.



FULL STORY ==========================================================================
It turns out sunflowers are more than just a pretty face: the ultraviolet colours of their flowers not only attract pollinators, but also help
the plant regulate water loss, according to new UBC research.


==========================================================================
The dense collection of yellow petals of a sunflower (technically an 'inflorescence', or collection of many flowers) is a familiar sight, but
it's hiding something from the human eye: an ultraviolet (UV) bullseye
pattern, invisible to humans but not to most insects including bees.

These bullseye patterns have long been known to improve the attractiveness
of flowers to pollinators by increasing their visibility. Now, UBC
researchers have found the same molecules that produce UV patterns in sunflowers are also involved in helping the plant respond to stresses
such as drought or extreme temperatures, in a new paper published
today in eLife, potentially providing clues to how plants can adapt to different climates.

"Unexpectedly, we noticed that sunflowers growing in drier climates
had flowers with larger UV bullseyes, and found that those flowers are
able to retain water more efficiently. This suggests that these larger
UV bullseyes help plants adapt to these drier environments," says lead
author Dr. Marco Todesco, a research associate at UBC's biodiversity
research centre and department of botany.

Dr. Todesco and his colleagues grew almost 2,000 wild sunflowers of two
species at the university in 2016 and 2019. They measured the sunflowers'
UV patterns, and analyzed the plants' genomes, and found that wild
sunflowers from different parts of North America had UV bullseyes of
very different sizes: in some, the bullseye was a thin ring, while in
others it covered the whole flower. Larger bullseyes were visited more frequently by bees, supporting previous research of other plant species.

The researchers found that a single gene, HaMYB111, was responsible
for most of the diversity in floral UV patterns. This gene controls the production of UV- absorbing flavonol compounds, which are also known to
help plants survive under different environmental stresses like drought
or extreme temperatures. Larger floral UV patterns that have more of these compounds could help reduce the amount of evaporation from a sunflower in environments with lower humidity, preventing excessive water loss. In
humid, hot environments, smaller UV patterns would instead promote
this evaporation, keeping the plant cool and avoiding overheating,
the authors say.

"Floral UV patterns appear therefore to play at least a dual role in adaptation; besides their well-known effect on enhancing pollination,
they also regulate water loss from flowers," says senior author Dr. Loren Rieseberg (he/ him), a professor in the department of botany and the biodiversity research centre. "That's not something you would necessarily expect a flower colour to do, and it exemplifies the complexity and
efficiency of adaptation -- solving two problems with a single trait." Sunflowers are cultivated for various purposes, including sunflower
oil production, a roughly US$20 billion dollar industry in 2020. This
research could help add to knowledge about how to attract pollinators, potentially increasing crop yields, says Dr. Todesco. "This work also
helps us understand how sunflowers, and potentially other plants, better
adapt to different areas or temperatures, which could be important in
a warming climate." The researchers also want to better understand how HaMYB111 regulates the size of UV bullseyes, and examine in more detail
how those patterns affect plant physiology as well as investigate how
exactly flavonol compounds affect water loss.

========================================================================== Story Source: Materials provided by University_of_British_Columbia. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Marco Todesco, Natalia Bercovich, Amy Kim, Ivana Imerovski,
Gregory L
Owens, O'scar Dorado Ruiz, Srinidhi V Holalu, Lufiani L Madilao,
Mojtaba Jahani, Jean-Se'bastien Le'gare', Benjamin K Blackman,
Loren H Rieseberg.

Genetic basis and dual adaptive role of floral pigmentation in
sunflowers. eLife, 2022; 11 DOI: 10.7554/eLife.72072 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220118104153.htm

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